38. R and D on hydrogen production by high-temperature electrolysis of steam

One of the objectives of the high-temperature engineering test reactor (HTTR) is to demonstrate the effectiveness of high-temperature nuclear heat utilization, which aims to extend the application of nuclear heat to non-electric fields, especially to hydrogen production. As part of the development of the hydrogen production processes, laboratory-scale experiments of a high-temperature electrolysis of steam (HTES) had been carried out with a practical electrolysis tube with 12 solid-oxide cells connected in series. Using this electrolysis tube, hydrogen was produced at the maximum density of 44 N cm3/cm2 h at a electrolysis temperature of 950 deg. C. Thereafter, to improve hydrogen production performance, a self-supporting planar electrolysis cell with a practical size (80 mm x 80 mm of electrolysis area) was fabricated. In the preliminary electrolysis experiment carried out at 850 deg. C, the planar cell produced hydrogen at the maximum density of 38 N cm3/cm2 h, and the energy efficiency was almost as high as that obtained with the electrolysis tube at 950 deg. C. However, both electrolysis tubes and planar cells did not keep their integrity in one thermal cycle. Durability of the solid-oxide cell against the thermal cycle is one of the key issues of HTES